Liu Yuzhang, Zhang Jun, Chang Jiang, Xie Shixiang, Zhao Yongsheng
Department of Civil Engineering, Tsinghua University, Beijing 100084, China.
Beijing Uni-Construction Group Company, Ltd., Beijing 100101, China.
Materials (Basel). 2022 Apr 10;15(8):2781. doi: 10.3390/ma15082781.
In the present paper, the effects of thermal insulation cover curing on the rise in temperature of concrete, and further on the mechanical properties of the concrete are measured experimentally. In the experiments, polyurethane foam boards of 100 mm thickness were used for thermal insulation, and three concrete strength grades of C30, C50 and C80, were used as concrete samples. Conventional standard curing, and two heat curing methods with a constant temperature of 40 °C and 60 °C were used for comparison. The pore structure of the cement paste subject to the different curing procedures, including insulation cover curing, heat curing and standard curing, was experimentally measured using mercury intrusion porosimetry. The test results show that rate of increase in compressive strength compared with standard curing is 22-34%, 16-26%, and 23-67%, respectively, for C30, C50, C80 concrete after being subject to 1 to 3 days thermal insulation cover curing in the initial period after concrete casting. As expected, initial heat curing of concrete will result in a reduction in the long-term strength of the concrete. At 28 days, the strength reduction rate compared with standard curing due to the insulation cover curing is 3.1-5.9%, 0.6-3.0%, 0-3.2%, respectively, for C30, C50, C80 concrete. By contrast, the compressive strength reduction compared with standard curing at 28 days is 8.6-10.5%, 8.6-9.1%, 4.7-5.6%, respectively, for C30, C50, C80 concrete after being subject to a constant heat curing of 40 °C and 60 °C in the initial period after concrete casting. Measurement of the pore structure of the paste subject to different curing procedures initially after casting shows that rising curing temperature leads to coarser pores, especially an increase in capillary pore fraction. Among the four curing methods used in the present study, the effect of insulation cover curing and low temperature (40 °C) heat curing on the capillary pore content is small, while the effect of high temperature (60 °C) heat curing is significant.
在本文中，对保温覆盖养护对混凝土温度升高的影响以及对混凝土力学性能的进一步影响进行了实验测量。在实验中，使用100毫米厚的聚氨酯泡沫板进行保温，并使用C30、C50和C80三种混凝土强度等级作为混凝土样本。采用常规标准养护以及40℃和60℃恒温的两种热养护方法进行比较。使用压汞法对经过不同养护程序（包括保温覆盖养护、热养护和标准养护）的水泥浆体孔隙结构进行了实验测量。试验结果表明，在混凝土浇筑后的初始阶段，C30、C50、C80混凝土经过1至3天的保温覆盖养护后，与标准养护相比，抗压强度增长率分别为22 - 34%、16 - 26%和23 - 67%。正如预期的那样，混凝土的初始热养护会导致混凝土长期强度降低。在28天时，C30、C50、C80混凝土由于保温覆盖养护与标准养护相比的强度降低率分别为3.1 - 5.9%、0.6 - 3.0%、0 - 3.2%。相比之下，C30、C50、C80混凝土在混凝土浇筑后的初始阶段经过40℃和60℃的恒温热养护后，在28天时与标准养护相比的抗压强度降低率分别为8.6 - 10.5%、8.6 - 9.1%、4.7 - 5.6%。对浇筑后最初经过不同养护程序的浆体孔隙结构测量表明，养护温度升高会导致孔隙变粗，尤其是毛细孔隙率增加。在本研究使用的四种养护方法中，保温覆盖养护和低温（40℃）热养护对毛细孔隙含量的影响较小，而高温（60℃）热养护的影响显著。
